Nitrogen

martinfan30

I TOLD YOU TO DO DONUTS ON THE STRIP NOW i see why your wife is pissed at you all the time YOU DONT LISTEN!!!!!! Give er another shot maybe lf rr with one and RF LR with another so You might be doing a few tests so well leave you alone.

martinfan30

Billahjack

Great thread here! This is so much better than the "which stickers should I put on my MotoX" that you see on other forums.

I haven't done any chemistry or physics for a while but I remember something about Nitrogen (N2) acting the most like an ideal gas. This means that it follows the physics and chemistry laws closer than other gasses which would make it more predictable. If you knew that your tires would heat up to 140 degrees under operation, you could adjust your starting pressure at a given starting temperature to obtain your optimum operating pressure when they heat up.

As for molecule size, the smaller the molecule, the easier it can slip through tubes, stems, tires, etc. If you were to put hydrogen in tires, you would probably find that you lost pressure over time quicker than shop air. Theoretically, the molecule size does not affect pressure because of the gas equation previously mentioned, PV=nRT. Pressure times volume = number of molecules times a constant times temperature.

However, there may be dynamic issues involved when introducing heat energy to a volume of hydrogen versus the same volume of Nitrogen. The larger the molecule, the slower it moves when comparing different gasses at the same temperature. The speed of movement for gas molecules is what creates the pressure.

Someone pointed out that shop air has a bunch of condensation. This is very true. I worked in a shop that installed an air dryer inline with their compressors. It was amazing how many gallons of water was separated from the lines each day.

I believe that this water in shop air is the biggest problem with tires. Water can become a vapor which affects the pressure as it transitions from vapor to liquid or vise versa. Since different sources can have different water vapor content, this could introduce widely varying pressure results under dynamic conditions. If you live in a humid environment, there will be more water in the air.

As for corrosion, I have never seen a car or truck rim with worse corrosion inside the rim than outside. Also, dirtbike tires have tubes so water corrosion would not affect them.

martinfan30

Great thread here! This is so much better than the "which stickers should I put on my MotoX" that you see on other forums.

I haven't done any chemistry or physics for a while but I remember something about Nitrogen (N2) acting the most like an ideal gas. This means that it follows the physics and chemistry laws closer than other gasses which would make it more predictable. If you knew that your tires would heat up to 140 degrees under operation, you could adjust your starting pressure at a given starting temperature to obtain your optimum operating pressure when they heat up.

As for molecule size, the smaller the molecule, the easier it can slip through tubes, stems, tires, etc. If you were to put hydrogen in tires, you would probably find that you lost pressure over time quicker than shop air. Theoretically, the molecule size does not affect pressure because of the gas equation previously mentioned, PV=nRT. Pressure times volume = number of molecules times a constant times temperature.

However, there may be dynamic issues involved when introducing heat energy to a volume of hydrogen versus the same volume of Nitrogen. The larger the molecule, the slower it moves when comparing different gasses at the same temperature. The speed of movement for gas molecules is what creates the pressure.

Someone pointed out that shop air has a bunch of condensation. This is very true. I worked in a shop that installed an air dryer inline with their compressors. It was amazing how many gallons of water was separated from the lines each day.

I believe that this water in shop air is the biggest problem with tires. Water can become a vapor which affects the pressure as it transitions from vapor to liquid or vise versa. Since different sources can have different water vapor content, this could introduce widely varying pressure results under dynamic conditions. If you live in a humid environment, there will be more water in the air.

As for corrosion, I have never seen a car or truck rim with worse corrosion inside the rim than outside. Also, dirtbike tires have tubes so water corrosion would not affect them.

ya, nice to have some intelligent conversation once in awhile, just wish i was capable!!!

thanks for the info billahjack! hey, you ever watch "feasting on asphalt" by alton brown????

jeanluconze

I'm a geophysicist and I can tell you that Nitrogen in your tires will absolutely make a significant difference in mileage and tire life . Of course, that's assuming your car is a perfect sphere in a vacuum. You're right, the dryness is the only benefit.

You could calc it out using the gas law if you're a loser:
PV = nRT
where
P is the pressure (SI unit: pascal)
V is the volume (SI unit: cubic meter)
n is the number of moles of gas
R is the ideal gas constant (SI: 8.3145 J/(mol K))
T is the thermodynamic temperature (SI unit: kelvin).

Personally, I'd fill with regular air and spend my lonely Saturday nights contemplating this much more complex equation instead:

brightman

ive raced pro stock and dirt late model cars for years and my son races go carts,and in all the race cars ive ever known of we have used nitrogen in the tires ,mainly because when the tires heat up the pressure does not change which is very crucial.we get a tank from the local welding supply store,like prax air,or what ever u have locally. the gas is very cheap,but the rental of the tank is somewhat more ,but it a one time rental.also we run a auto repair service and all the major publications recomend nitrogen in the tires,especially the new cars because as of 2008 model year all cars will be manditory tire pressure monitors in the wheel.so its not really is it better,its if u can do it, u should,just my humble opinion,and most everyone else actually.

martinfan30

ive raced pro stock and dirt late model cars for years and my son races go carts,and in all the race cars ive ever known of we have used nitrogen in the tires ,mainly because when the tires heat up the pressure does not change which is very crucial.we get a tank from the local welding supply store,like prax air,or what ever u have locally. the gas is very cheap,but the rental of the tank is somewhat more ,but it a one time rental.also we run a auto repair service and all the major publications recomend nitrogen in the tires,especially the new cars because as of 2008 model year all cars will be manditory tire pressure monitors in the wheel.so its not really is it better,its if u can do it, u should,just my humble opinion,and most everyone else actually.

ya i know some of the more scientific types here dont like it, but im with ya due to the fact we know is less likely to leak out, plus its dry. also it helps when its free!

brightman

cleonard

I'd be right there with you if it was free for me. I can't say that I have had a terrible rash of problems using air for the last 30+ years.

For the majority of people it is not. Most places charge an insane $5 per tire for 10 cents of nitrogen. Even though it may leak less, it does leak. Is that another $5/tire when it needs a top off? I change my tire pressures in my truck when I really load up the bed, another $5/tire? That is the part of the equation that I don't get. I bet if you ask the boss his biggest reason for buying the nitrogen generator is the $4.90/tire he can make in pure profit. OK maybe the capital and operating costs are more than 10 cents per tire, but it still is mostly profit.

The sensors on the tire inflation warning systems may be a very valid reason for nitrogen use. It will keep them from fouling and I'm sure they will be $$$ to replace. Once again it is not something magical with the nitrogen that makes it better, it is the filtering and dryness. I thought that only the high end cars will be getting pressure measuring devices. The low end cars will just use the ABS sensors to sense a low pressure tire. Low pressure means that the tire gets a flat spot and it doesn't go as far in a single rotation. The difference in tire rpm can be used to signal the driver.

martinfan30

I'd be right there with you if it was free for me. I can't say that I have had a terrible rash of problems using air for the last 30+ years.

For the majority of people it is not. Most places charge an insane $5 per tire for 10 cents of nitrogen. Even though it may leak less, it does leak. Is that another $5/tire when it needs a top off? I change my tire pressures in my truck when I really load up the bed, another $5/tire? That is the part of the equation that I don't get. I bet if you ask the boss his biggest reason for buying the nitrogen generator is the $4.90/tire he can make in pure profit. OK maybe the capital and operating costs are more than 10 cents per tire, but it still is mostly profit.

The sensors on the tire inflation warning systems may be a very valid reason for nitrogen use. It will keep them from fouling and I'm sure they will be $$$ to replace. Once again it is not something magical with the nitrogen that makes it better, it is the filtering and dryness. I thought that only the high end cars will be getting pressure measuring devices. The low end cars will just use the ABS sensors to sense a low pressure tire. Low pressure means that the tire gets a flat spot and it doesn't go as far in a single rotation. The difference in tire rpm can be used to signal the driver.

i prob. wouldnt use it if i had to pay for it too. most all our our line uses TPWS. we are also getting away from using speed sensors and strictly using individual tire sensors. they are about 150 bucks.

motometal

there is a benefit to having the pressure vary more, like it does with "wet" air, at least for some applications. If you are running a car or bike on a paved course, it takes a certain number of laps to get the tires up to temp, for good traction. A tire with less pressure will build more heat, faster...so to some degree, this is self-adjusting...as heat builds, so does pressure, which tends to support a cooler running tire (due to less heat being generated by tire friction).

So the negative with air is not so much HOW MUCH it builds pressure, but how consistently the pressure builds up, which is related to the water vapor content of the air.

With "average" air, the rule of thumb is that you are looking for 10% increase in pressure from cold to hot. So, 20 psi cold and 22 psi after some hot laps.

cleonard

So the nitrogen in your tires somehow avoids following the ideal gas law, i.e. it doesn't build pressure as the temps increase?

That's just what I said if you look back in this thread. It turns out that the issue isn't nitrogen vs. air, it is dry nitrogen vs air with water. Look at Martinfan's tests with dried shop air vs nitrogen and his pressure results are almost exactly the same. When you read the marketing materials from the companies that sell these nitrogen generator systems it sure does read like they are selling magic.

The big difference comes with racers. They run as hot as 200F on the tires. If there is any liquid water in the tire the pressure form the liquid to vapor water could be as much as an additional 12 or 13 psi if there is enough water in there. I live in the desert and I am amazed at how much liquid water comes out of my compressor. When you are concerned with 1/4 psi in your tires a few psi from water can really hurt your chances of winning. Sure they could use a drier on the compressor, but it is so much easier just to fill with a high pressure nitrogen tank. The tank doesn't need electricity and it just about 100% reliable.

motometal

I'm ashamed to say I read each and every post in this thread. I was just tying the "PVNRT" posts together with his post.

And like mentioned before, once you have the equipment, nitrogen is very cheap...in fact, for companies that must have a tank or generator anyway, it's not unheard of to plumb the entire plant with compressed nitrogen in place of compressed air, and with air tools you are going through a lot of it. So yah, at $5/tire or $30 for four, it's a high profit margin.